Closed air pressure system having an emergency shut off

ABSTRACT

There is provided an emergency motor shut off for a closed air system having a low pressure threshold and a high pressure threshold. In a preferred embodiment, the closed air system includes a compressor and motor for charging the pressure of the system. Typically, any suitable electric power source provides power to the motor. A pair of electric contactorss electrically disposed between the power source and the motor are pneumatically controlled to allow electric current to either pass through or to prevent current from reaching the motor. A timer determines the run time for a single run cycle of the motor. A shut off that is responsive to the timer impedes the flow of electric current to the motor after a predetermined amount of run time. The timer is reset to zero after each run cycle of the motor. Typically the shut off comprises a relay timer having an internal relay. The invention also provides for an alarm to signal when the system when the predetermined amount of time is reached on the timer.

FIELD OF THE INVENTION

[0001] The present invention relates generally to closed pressure systems, and more particularly to a compressor system having an automatic shutoff upon failure to charge properly.

BACKGROUND OF THE INVENTION

[0002] In closed pressure systems, such as those used in auto repair garages, a motor drives a compressor which in turn raises the pressure of the system. A power source such as 110, 220 or 440 volts single or three phase or any other suitable power source typically provides power to the motor.

[0003] In one type of system, the power source includes two legs at 110 volts each and a neutral and equipment ground. Each 110 volt leg runs through a pair of pressure controlled contacts. When the system reaches a low pressure threshold, such as 145 psi, the pressure controlled contacts close thereby allowing the electric current to reach the motor. Once the system charges to a high pressure threshold, such as 175 psi, the pressure controlled contacts open thereby shutting electric current from the motor.

[0004] One problem with this type of system is that the closed pressure system could have a rupture or leak thus making it difficult if not impossible to reach the high pressure threshold. In this situation, the motor runs indefinitely until it is manually switched off. If the motor is not manually switched off it will either burn out or heat to such a degree as to cause a fire. Either way the motor, if not the entire garage, must be replaced.

[0005] In garages that offer waste oil burning services, it is recommended that a compressor maintain a certain level of pressure twenty four hours a day seven days a week. Therefore, the motor runs even when there are no personnel present to monitor the system.

[0006] In well pump systems, it is important to maintain a certain well pressure for water to flow efficiently throughout. For example, a farmer must have well pressure to insure that the cows have water to produce milk. Once again the motor runs even when nobody is present to monitor the situation. If the pump motor were to burn up, it could have disastrous effects on the farmers livestock.

SUMMARY OF THE INVENTION

[0007] It is therefore an object of the present invention to improve the art of closed pressure systems.

[0008] It is another object of the present inventions to provide fire protection for buildings that house closed pressure systems.

[0009] It is still another object of the present invention to provide automatic protection for a motor that drives a closed pressure system.

[0010] It is yet another object of the present invention to provide an automatic shut off for the motor to prevent the motor from burning out.

[0011] It is still yet another object of the present invention to save unnecessary electrical energy for a closed pressure system that contains faults.

[0012] It is yet a further object of the present invention to provide an alarm signal for a closed pressure system that contains a fault.

[0013] It is yet still a further object of the present invention to provide additional fire protection for motor driven applications.

[0014] It is still yet a further object of the present invention to shut off and provide an alarm signal upon the closed pressure system obtaining a fault.

[0015] These and further objects are obtained in accordance with a closed air system having a low pressure threshold and a high pressure threshold. In a preferred embodiment, the closed air system comprises a compressor and a motor for charging the pressure of the system. Typically, any suitable electric power source provides power to the motor. A pair of electric contacts electrically disposed between the power source and the motor are pneumatically controlled to allow electric current to either pass through or to prevent current from reaching the motor.

[0016] A timer determines the run time for a single run cycle of the motor. An electric shut off that impedes the flow of electric current to said motor is responsive to the timer. The timer is reset to zero after each run cycle of the motor. Typically the electric shut off includes a relay timer having a relay in each electric input power line. The relays are opened after a predetermined amount of time is sensed by the timer relay. The invention also provides for the relay timer to trigger an alarm after sensing the predetermined amount of time.

[0017] A toggle switch allows the motor to run in either a timed or untimed state. The toggle switch determines which state by allowing the electric input power lines to bypass the relay timer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

[0019]FIG. 1 is a block diagram of the closed pressure system of the prior art;

[0020]FIG. 2 is a block diagram of a preferred embodiment of the closed pressure system of the present invention;

[0021]FIG. 3 is block diagram of the method of the present invention;

[0022]FIG. 4 is a block diagram of a housing faceplate in accordance with the closed pressure system of the present invention; and

[0023]FIG. 5 is a block diagram of an alternative embodiment of the closed pressure system of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0024] Referring now to FIG. 1, there is shown a closed pressure system 10 of the prior art. By way of example, pressurized air is contained in a closed tubing 12 to be released for applications such as providing power to drive tools, lifts and even to burn waste oil. For waste oil applications it is desirable that the pressure be maintained above a low pressure side for twenty four hours per day. In one non-limiting example, the pressure of the air is maintained at 175 pounds per square inch on the high side, hereinafter high pressure threshold, and 145 pounds per square inch on the low side, hereinafter low pressure threshold.

[0025] Once the air pressure of the system 10 falls to the low pressure threshold a compressor 14 driven by a motor 16 raises the air pressure of the system 10 until the high pressure threshold is reached. The motor 16 is powered by two hundred and twenty volts of single phase power carried along wires 18 and 20.

[0026] A pneumatic controller 22 closes a first contact 24 and a second contact 26 at the low pressure threshold, thereby allowing electric current to power the motor 16. The current powers the motor 16 until the compressor 14 raises the system pressure to the high pressure threshold.

[0027] At the high pressure threshold, the pneumatic controller 22 opens the first and second contacts 24 and 26 to cut the electric current to the motor 16. The system 10 now discharges pressure through normal use until the low pressure threshold is once again reached.

[0028] One problem inherent in this system 10 occurs when a rupture arises in the closed tubing 12. The pressure of the system 10 now falls to the low pressure threshold, but it is impossible to return to the high pressure threshold due to the leak. As a result, the motor 16 continues to run indefinitely until it is manually turned off. Failure to manually turn off the motor 16 in time causes the motor 16 to overheat which invariably destroys the motor 16. Overheating the motor 16 can also cause a fire which can destroy an entire facility.

[0029] In some situations, a heater coil 27 senses the temperature of the motor 16 and stops electric current from reaching the motor 16 when the motor 16 becomes too hot. However, at this point the compressor 14 and the motor 16 are invariably damaged.

[0030] Turning now to the present invention which will be described in accordance with a closed pressure system 17 depicted in FIG. 2, the closed tubing 12 contains pressurized air which is to be released for applications such as providing power to garage type tools (not shown) or for keeping primed a well pump (not shown).

[0031] As described above the motor 16 drives the compressor 14 to charge the system from the low pressure threshold to the high pressure threshold. Two hundred and twenty volts of electric current provides power to the motor 16 through conductors 18 and 20 each carrying one hundred and ten volts. Yet again as described above the pneumatic controller 22 closes and opens the first and second contactors 24 and 26 to power and cut power to the motor 16.

[0032] To prevent the motor 16 from running indefinitely a timing relay device 30 is electrically connected between the power source 25 and the motor 16. In FIG. 2, the timing relay device 30 includes an internal relay (not shown) that breaks conductor 18 before first contactor 24. In an alternative embodiment depicted in FIG. 5, the timing relay device breaks conductor 18 after first contactor 24.

[0033] The timing relay 30, externally powered through connector 37, operates by tracking time and then performing a certain function when a predetermined set run time is reached. The timing relay 30 includes an internal timer and actuator (not shown) that are connected across either contactor 24, 26 or an auxiliary contactor not shown. The internal timer continuously accumulates time until electric power to it is discontinued, at which point the accumulated time resets to zero. The actuator opens the internal relay upon reaching the set run time, which cuts electric power to the motor 16.

[0034] A toggle switch 32 is electrically inserted into the system 17 so that it allows current to bypass the timing relay device 30 when the toggle switch 32 is in the untimed (ON) state. The toggle switch 32 is designed so that it operates at one of two states (ON/OFF) until it is changed. The user sets the toggle switch 32 for either a timed or untimed (bypass) run. Obviously, the toggle switch 32 is initially set to the timed (OFF) state so that the timing relay device 30 is operable.

[0035] In other words, the timing relay 30 in concert with the toggle switch 32 acts as a safety cutoff for the motor 16 having bypass capability. This prevents destruction of the motor 16 in case of a system leak or a fire if the motor 16 overheats because of non-stop running.

[0036] Normally it takes the motor 16 a predetermined amount of time to force the compressor 14 to charge the system 10 from the low pressure threshold to the high pressure threshold. Therefore, the timing relay 30 set run time must be greater than amount of time it takes the motor 16 and compressor 14 to complete a single charging cycle from low pressure threshold to high pressure threshold with an operable system 10.

[0037] At the high pressure threshold the pneumatic controller 22 opens the contactors 24, 26 thereby stopping the flow of electric current through the system 17. As a result, the relay timer 30 resets itself to zero time.

[0038] According to the diagram depicted in FIG. 2, when the toggle switch 32 is closed, electric current bypasses the timing relay 30 thus forcing the system 17 to operate in accordance with the prior art.

[0039] When the toggle switch 32 is open, the electric current flows through the timing relay 30 thus gaining the above described features, functions and advantages of the present invention.

[0040] In operation and according to a preferred embodiment, the invention shall now be described with reference to FIG. 3. Considering a system 10 charged to the high pressure threshold of 175 pounds per cubic inch, the pneumatic controller 22 forces open the contacts 24 and 26. Consequently, no power is provided to the relay timer 30 thereby initializing the relay timer 30 to zero time, shown in step 40.

[0041] As the system 10 operates the pressure gradually decreases to the low pressure threshold of 145 pounds per cubic inch. At this system pressure, the pneumatic controller 22 forces contacts 24 and 26 closed, shown in steps 42 and 44. The relay timer 30 begins counting time, shown in step 46. The motor 16 and compressor 14 are now charging the pressure within the system 17.

[0042] Now two competing interests unfold. In a properly working system 17 with no ruptures, the system pressure will reach the high pressure threshold, step 48, before the set run time is reached, step 52. In one practical example, it takes the system 17 approximately two and a half minutes to charge to the high pressure threshold. Therefore, the predetermined amount of time is set for four minutes.

[0043] If the system 17 is working properly, then upon reaching the high pressure threshold the pneumatic controller 22 forces the contactors 24 and 26 open, shown in step 50. Thus, the relay timer 30 is initialized to zero time as depicted in step 40.

[0044] In a ruptured or leaky system 17, the high pressure threshold will never be attained upon charging. As a result, the predetermined amount of time will be reached before completely charging the system 17, shown in step 52. At this point, the relay timer 30 forces open a pair of internal relays thereby cutting power to the motor 16, shown in step 54.

[0045] The contacts 24 and 26 are still closed because the high pressure threshold was never attained. In certain circumstances it may be desirable to run the motor 16 longer than the set run time. For example, in sandblasting applications it is desirable to run the motor 16 for fifteen continuous minutes. The user simply forces the toggle switch 32 to the untimed (ON) state to override the relay timer 30. As a result, the motor 16 runs continuously with the toggle switch 32 acting as an override switch.

[0046] The relay timer 30 activates an alarm 36 when the set run time is reached, shown in step 56. The alarm could be any type of audio or video alarm.

[0047]FIG. 4 depicts a housing faceplate 60 for the closed pressure system 17. The toggle switch 32 disposed through the faceplate 60 gives the user convenience access to set either a timed or a bypass run as previously described. A reset button 62 allows the timing relay 30 to be automatically reset.

[0048] An alert indicator 64 illuminates when the pressure system 17 fails or “times out.” A normal indicator 66 illuminates when the system 17 is in normal use. Finally, a bypass indicator 68 illuminates when the toggle switch is set to bypass or “override.”

[0049] Various changes and modifications, other than those described above in the preferred embodiment of the invention described herein will be apparent to those skilled in the art. While the invention has been described with respect to certain preferred embodiments and exemplifications, it is not intended to limit the scope of the invention thereby, but solely by the claims appended hereto. 

What is claimed is:
 1. A closed air system having a low pressure threshold and a high pressure threshold, said closed air system comprising: compression means for raising the pressure of said system; a motor for driving said compression means; an electric power source for providing electric current to said motor; timing means for determining the run time for a single run cycle of said motor; an emergency shut off means that impedes the flow of electric current to said motor, said emergency shut off means responsive to said timing means; and timing reset means for resetting the run time to zero after each run cycle of said motor.
 2. The system of claim 1, wherein said timing reset means includes a counter and at least one electric contactor, wherein the run time is reset to zero when said at least one electric contact opens.
 3. The system of claim 1, wherein said emergency shut off means further includes at least one relay electronically disposed between said power source and said motor, said relay opening after a predetermined run time is determined by said timing means.
 4. The system of claim 3, further including bypass means for bypassing said emergency shut off means.
 5. The system of claim 1, further including at least one alarm, said alarm responsive to said emergency shut off means.
 6. A method for protectively shutting down a closed pressure system wherein the system fails to charge to a high pressure threshold after a predetermined charging time, wherein a motor driven compressor begins raising the air pressure once the air pressure of the system reaches a low pressure threshold, said method comprising: counting means for determining an amount of run time of a single run cycle of the motor; resetting means for resetting the counting means to zero if a predetermined run time is not reached during the single run cycle of the motor; and shutting down said motor after a predetermined amount of time is determined by said counting means during said single run cycle of said motor, wherein said predetermined amount of time is greater than the time it normally takes for the system to properly charge to the high pressure threshold.
 7. The method of claim 6 wherein said setting a timing means further includes the step of cutting power to a timing relay device.
 8. The method of claim 6 wherein said determining the run time of a single run cycle of said motor further includes the step of determining the amount of time that continuous electric current passes through a timing relay device.
 9. The method of claim 6 wherein electric current running from a power source through a timing relay device controls the motor, and wherein the step of shutting down said motor further includes the step of opening at least one internal relay of said timing relay device.
 10. The method of claim 6 further including the step of signaling an alarm after said shutting down step.
 11. A closed air system having a low pressure threshold and a high pressure threshold, said closed air system comprising: compression means for raising the pressure of said system; a motor for driving said compression means; an electric power source for providing power to said motor; at least one electric contactor electrically disposed between said power source and said motor; a pressure determining means for determining the pressure of said system; a first shut off means which opens said at least one electric contact, said first shut off means responsive to said pressure determining means; timing means for determining the run time for a single run cycle of said motor; a second shut off means that impedes the flow of electric current to said motor, said second shut off means responsive to said timing means; and timing reset means for resetting the run time to zero after each run cycle of said motor.
 12. The system of claim 11, wherein said timing reset means includes a counter and at least one electric contactor and the run time is reset to zero when said at least one electric contactor opens.
 13. The system of claim 11, wherein said second shut off means further includes at least one relay electronically disposed between said power source and said motor, said relay opening after a predetermined amount of time is determined by said timing means.
 14. The system of claim 13, further including bypass means for bypassing said shut off means.
 15. The system of claim 11, further including at least one alarm, said alarm responsive to said second shut off means.
 16. The system of claim 11, further including closing means that closes said at least one electric contact when the system air pressure reaches the low pressure threshold.
 17. The system of claim 11, further including opening means that opens said at least one electric contact when the air pressure reaches the high pressure threshold. 